Means for trimming noncircular cans



Feb. 25, 1941. 1.. GLERUM ,2 2,8 9

MEANS FOR TRIMMING NONCIRCULAR CANS Filed April 24, 1940 i; f?0%2VZZ/07V Patented F eb. 25, 1941 UNITED STATES 2,232,849 MEANS FORTRIMMING NONGIRCULAR.

CANS

Irvin L. Glerum, Chicago, Ill., assignor to Edwin I.

Guthman & Co. Inc.

tion of Illinois Chicago, 111., a corpora- Application April .24., 1940,Serial No. 331,447 8 Claims. (01. l64 fi) This invention relates tomeans for trimming the ends of noncircular metal cans 0r pipes andparticularly of cans having a generally rectangular cross section withrounded. corners.

In many instances, it is desirable to have cans within which variouselements may be disposed. These cans may have various cross sections.Thus in many radio receivers, cans having a rectangular cross section.with rounded corners are quite frequentlyused. Such cans are generallydrawn or extruded and then trimmed down to size. Since such cans must behandled by operators, it is necessary that the trimmed edges r of thecan be smooth and free of burrs.

Various methods of trimming such cans have been used with indifferentresults. As a rule, the can is supported by dies, one on the inside andthe other on the outside of the can to support the metal throughout itsentire perimeter. Cans 20 supported in this manner have been out by acircular saw. However, this is relatively expensive and requiresconsiderable upkeep of the saw.

Another method of trimming the cans involves theuse of a straight cutterextending outwardly from a revolving shaft. The can, supported betweendies, is fed toward the cutter with the plane of rotation of the cutterperpendicular to the axis of the can. Such a method is unsatisfactoryfor the reason that near the rounded corners-burrs are formed which cutand tear the operators fingers. The metal is also distorted, makingremoval from the dies diflicult and making it impossible for subsequentuse on automatic machines or other dies.

I have determined that the unsatisfactory operation of such a cutter iscaused by excessive variation of the angle of attack between the cuttingedge and the tangent to the surface of the can at the cutting point.Thus if the cutting tool is perpendicular to this tangent, asubstantially pure cutting action results. This is true with a radialcutter operating on circular cans. However, if this angle varies, theforce of the cutter on the can metal may be resolved into twocomponents. One component, which may be called the cutting component, isparallel to the tangent to the can metal at the point of cutting.

50 The other component is perpendicular to this cutting component,although in the plane of rotation of the cutter. This secondperpendicular component cooperating with the dies holding the can metalresults in a shear action.

It is evident that in shearing metal, there is some flow of metal and itis quite easy todetermine from inspection of the sheared edge which waythe shearing force is applied. If this shearing force is reversed sothat at some part 60 of the metal the shearing force is directed awayfrom the can interior and at other partstoward the can interior, thebending and flow of the metal along. the sheared edge will be changedand burrs will result. This is true irrespective of how carefully thedies fit.

- The action of a straight radial cutter on a can having a rectangularcross section results in an excessive variation of the shear force, thechange in absolute value and sign of the shear component, considered asa vector, being so great that .1 burrs result. j

By the invention hereinafter disclosed, I have provided one meanswhereby the cutting angle is maintained at a substantially constantvalue. Another; and-preferred means is disclosed where- 5 in variationof the-cutting angle is permitted but the cutting angle range issuchthat the shear component always retains thesame algebraic sign. Acutter so designed to fulfill these conditions-has been found to operatein a highly satisfactory manner and: trims the edges smoothly andquickly.

Referring to the drawing:

Figure 1 shows one form of the invention Where a substantially constantcutting angle is 2:5 maintained;

Fig. 2 shows a preferred modified form wherein a curved cutter is used;and

Fig. 3 is a top view looking down upon Fig. 2.

Referring first to Fig. 1, a can 10 having straight sides H and roundedcorners l2 and having a generally rectangular cross section is supportedbetween an inside die 13. and an outside die [4, both dies fitting thecan surfaces snugly. It is understood, of course, that both dies are ofa suitable length and mounted in a suitable manner so that the can maybe moved lengthwise thereof from the cutter.

The end face of outer die I4 is provided with a cam groove l6 whichsubstantially parallels the 40 outline of the can or pipe. Riding inthis groove I6 are a pair of rollers l1 and I8 preferably close togetherand both rigidly fastened to a member Zilsupporting a cutter 2| at oneend thereof. The angle between the cutter and the can edge may have anysuitable value. It is understood of coursethat member 20 and rollers l1and It are prevented from moving perpendicular to the plane of cutterrotation, here the plane of the paper, although free to travel aroundthe groove. A shaft 23 and rod 24 on the shaft furnish the motive powerfor pushing the cutter assembly along the groove.

The earn groove having a larger radius of curvature than the can edgepermits the two rollers to travel therein and maintain the cuttersubstantially at a constant angle to the can material. By feeding thecan toward the cutter or vice versa, the ends may be trimmed off. It isunderstood of course that if the can has a difso ferent outline thanrectangular that the groove will be s milarly changed.

Referring to Figs. 2 and 3, a preferred form of this invention is shown.Here the can is mounted as before between dies. Inner die I3 may beeliminated, if desired, since the shearing force is directed towardouter die H, as will be evident later. Cutter 30 having a spiral cuttingedge 3| is provided. As shown in the original drawing, this cutter isdrawn full scale and is adapted to operate upon cans whose sides arebetween one and one-eighth inches and two inches.

The cutter 30 may be rotated by a lathe spindle or the like and part l4may be held by a chuck as all that is necessary is to present the cutterto the work. Similarly, part 23 may also be revolved in the same way.The machine to hold parts 30 and I4 is omitted to simplify the case.

The direction of rotation of this cutter-it is evident that in bothforms the cutter may be stationary andthe can rotated-is such that astationary vector ending at the spiral would be elongated. Forconvenience this direction of rotation may be termed a spiral generatingdirection.

It will be noted that in this spiral, there is present a cuttingcomponent parallel to the tangent to the can material at the point ofcutting and a shear component perpendicular to the tangent and alwaysdirected outwardly away from the can interior.

Almost any spiral shaped cutter may thus be used. It is only necessarythat the spiral should have two points whose radius vectors arerespectively small enough and large enough to accommodate the nearestand furtherest points on the can. In a can having the cross sectionshown, these points (assuming that the cutter center shaft is coincidentwith the can center) are onehalf of the smallest side and diagonalrespectively.

These two points on the cutter may have any desired angular distancebetween them, the angle being measured vectorially.

The spiral as shown here is not necessarily a true mathematical spiralin the sense that it has a continuous mathematical equation. While sucha spiral may be used, it is easier to draw an arbitrary spiral betweendesired points. The curve of the cutter as disclosed here was obtainedby merelyusing the curves on the socalled French curve used bydraftsme'n and consisting of a transparent solid having a large numberof differently shaped edges cut thereon.

It is preferred however to use outer edge 3| in the manner shown in Fig.2 since the scrap may be more easily disposed of and does not clog upthe cutter.

It will be understood that by the term spiral generating direction ismeant a spiral cutting edge revolving as disclosed in Fig. 2 so that theabsolute value of the radius vector is increasing.

What is claimed is:

1. In a machine for trimming the ends of noncircular metal cans orpipes, the combination of means for holding such a non-circular canincutting position, a cutter, means for moving said cutter relative tosaid can about an axis parallel to the length of the can and lyingwithin the cross sectional area of the can, and means for maintainingthe cutting angle substantially constant.

2. In a machine for trimming the ends of noncircular metal cans orpipes, the combination of means for holding such a non-circular can incutting position, a cutter, means for moving said cutter relative tosaid can about an axis parallel to the length of the can and lyingwithin the cross sectional area of the can, and means for maintainingthe cutting angle within predetermined limits sufficient to provide asmooth out edge around the can.

3. In a machine for trimming the ends of noncircular metal cans orpipes, the combination of means for holding such a non-circular can incutting position, a cutter, means for moving said cutter relative tosaid can about an axis parallel to the length of the can and lyingwithin the cross sectional area of the can, and means for maintainingthe cutting angle so that the force component perpendicular to the cansurface at the point of cutting exerted by the cutting edge alwayspoints in the same general direction with reference to the can interior.

4. In a machine for trimming the ends of metal cans or pipes having arectangular cross section, the combination of means for holding such acan in cutting position, a cutter, means for moving said cutter about anaxis concentric with the axis of the can, and means for maintaining thecutting angle within such limits that the component perpendicular to thecan surface at the point of cutting due to the force exerted by thecutter always points in the same general direction with reference to thecan center.

5. In a machine for trimming the ends of metal cans or pipes having agenerally rectangular cross section, the combination of means forholding such a can in cutting position, a cutter having a predeterminedangle to the can material for cutting the same, and means for movingsaid cutter relative to said can about the can axis, said can movingmeans including a guiding member having substantially a congruent shapeto said can cross section and cOntrolling the cutter angle to maintainthe same constant during its travel with respect to the can.

6. In a machine for trimming the ends of metal cans or p pes having asubstantially rectangular cross section, the combination of meansincluding a die around the outer surface for holding such a can incutting position, a cutter having a generally spiral cutting edge, andmeans for rotating said cutter about said can axis, said cutter havingits cutting edge so disposed and the cutter being turned in such adirection that the shear component exerted by the cutter upon the can isalways directed outwardly from theinterior of the can.

7. The combination of claim 6 wherein said cutting edge is on the outerleading side of the gutter and rotated in a spiral generating direcion.

8. In a trimming machine, the combination of means for retaining agenerally rectangular can Or pipe in cutting position, and a cutterrevoluble in a plane parallel to a can section and about an axisperpendicular to the can section and lying within the cross sectionthereof, said cutter having a generally spiral cutting edge of acurvature to maintain the shear component direction generally the samewith respect to the can interior during a cutting cycle, said retainingmeans including a die along that can surface toward which the shearcomponent points.

IRVIN L. GLERUM.

